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XLIII. The Viscosity of Liquids. 

 By Owen Glynne Jones, B.Sc* 



THE object of this paper is to point out a method for the 

 accurate determination of the viscosity of highly viscous 

 liquids. The author would prefer to delay the publication of 

 most of his results till the experiments are completed. The 

 advantages and disadvantages of the method, and its applica- 

 bility to the determination of viscosities such as those of 

 alcohol and water, are not yet entirely ascertained, but such 

 of these points as have already suggested themselves will be 

 noticed at the end of the paper. 



Sir G. Stokes has long since shown that if a sphere 

 moves vertically in an infinite liquid under the action of 

 gravity only, it in course of time assumes a constant speed : 



where a is the radius of the sphere, a its density, p that of the 

 liquid in which it moves, and /x the viscosity of the liquid. 

 The equation assumes that there is no slipping at the surface 

 of the sphere, i. e., that the coefficient of sliding-friction is 

 infinite. The effect of such sliding-friction would be to 

 modify the equation thus : 



where /3 is the coefficient of sliding-friction. 



The method employed by the author consists in the mea- 

 surement of the downward speed of a sphere of mercury 

 through the viscous liquid. The amount of mercury used is 

 taken sufficiently small to render possible the measurement, 

 correct to "1 per cent., of the time taken to pass through a 

 distance of about 25 centim. This also renders legitimate 

 the assumptions that the mercury remains spherical during 

 its motion, and that the liquid in an ordinary burette about 

 1*5 centim. internal diameter is for purposes of calculation 

 of infinite extent, the motion of such a sphere falling down 

 the burette along its centre line being unaffected by the sides 

 of the vessel. 



The burette is jacketed with water kept as nearly as 

 possible at constant temperature. The temperature of water 

 direct from the main was observed last autumn to vary to an 



* Communicated "by the Physical Society : read February 9, 1894. 



